Is abstract class field in python possible?

Attribute trouble when instantiating a class in Python 2.7

• I'm having maddening problems creating objects in Python. Details inside This is the beginning of a class definition I'm using: class popObj(object): """standalone class mainly holding list of binary trees and generation""" def _init_(self): #initializes two empty lists and a generation tracker self.biTrees=[None]*POP self.selectedTrees=[None]*POP self.generation = 0 In the main module of the program, then, I call: population=popObj() I'm able to put objects into the list at population.biTrees[] with no problem. But when I try to do anything with population.selectedTrees or population.generation, I get this error: AttributeError: 'popObj' object has no attribute 'selectedTrees' What's going on? This is driving me nuts. I recognize that my class definition isn't very elegant, but I can figure out why some of the attributes don't exist.

• Answer:

  You've misnamed "__init__", it looks like. It needs to have two underscores around it, not one. (underscore-underscore-init-underscore-underscore). So __init__ isn't running and it isn't creating those attributes. Possibly you're accidentally creating biTrees by accident somewhere else which is why that ones's working and the others aren't.